In the hyper-crowded skyscraper districts of Shanghai, densities can approach 125,000 people per square mile. Giant buildings often function as vertical suburbs, muting the spontaneous encounters that provide cities with so much of their social, intellectual and commercial energy. People live their lives indoors in such places, wearing paths between their offices and the food courts, always seeing the same people.

In terms of innovation and creative impetus, Shanghai pales in comparison to New York, London, Paris and Milan, not to mention high-tech hubs like Silicon Valley, the Bay Area, Seattle, Boston, Austin and North Carolina’s research triangle, all of which have much lower densities.

He goes on to explain that it is the “Jacobs Density,” named for—yep—Jane Jacobs, that makes these places successful. Not just a lot of people, but a lot of people interacting (notice Dallas and Phoenix, two of our biggest cities, don’t make the cut).

And even within our well-balanced cities, where does the real magic happen?

Look at New York City. Its hubs of innovation aren’t the great skyscraper districts that house established corporate and financial headquarters, media empires and wealthy people (an increasing number of whom are part-time residents who hail from the ranks of the global super-rich). The city’s recent high-tech boom—500 start-ups in the last half decade, among them Kickstarter and Tumblr—is anchored in mid-rise, mixed-use neighborhoods like the Flatiron District, Midtown South, Chelsea and TriBeCa.

Not to mention Brooklyn.

This may not be entirely fair to the office rats clamoring around Midtown and Downtown because many of them do wind up in the Village, Chelsea and Park Slope after hours, relaxing, rejuvenated, sharing ideas. The Garment District, Times Square, the museums and non-profits uptown, all are home to smart people living ontop of one another.

And if anything, the administration wants to use the bigger buildings to help fund improvements to the streetscape in Midtown, from wider subway platforms to the new plans for Vanderbilt Avenue becoming a grand pedestrian mall. Just so long as we do not wind up with a string of Zuccotti Parks, everything just might work out.